Based on our subgrouping according to ECG patterns men were
Based on our subgrouping according to ECG patterns, men were predominant in the Br, ER, or Br–ER group compared with the true IVF group (Table 1). This sex difference was also noted in previous reports [15–17] and may be partially due to different levels of Ito channel expression between sexes . In this regard, we recently reported that 2 novel KCNE5 mutations produced gain-of-function effects on Ito. Because KCNE5 is located in the X-chromosome, it is interesting that all 3 male mutation carriers were symptomatic and 2 of them displayed Br, whereas only 2 of the 8 female carriers were symptomatic, none of whom had a Br pattern.
Conclusion We identified no KCNJ8 gene mutation in our IVF and JWS patients. Therefore, KCNJ8 seemed to be not a major gene responsible for the JWS or IVF cases in Japan.
Conflict of interest
Introduction Brugada syndrome is characterized by ST elevation in the right precordial leads on electrocardiogram (ECG) and poses a high risk of sudden cardiac death (SCD), for which the mean age is approximately 40yr . Brugada syndrome is thought to account for 4–12% of all cardiac deaths and at least 20% of deaths in patients with a structurally normal heart . The syndrome follows an autosomal dominant mode of transmission with incomplete penetrance. Mutations in the SCN5A gene encoding the cardiac sodium channel and other types of ion Cilengitide (ICaL, IKs, and Ito) have been reported as the genetic basis of the disease [3–8]. Because these ion channels are not restricted to ventricular tissue, the electrical abnormality might also affect the atria, and indeed, an association between supraventricular tachyarrhythmias and Brugada syndrome has been reported [9–11]. However, the incidence and clinical consequences of supraventricular tachyarrhythmia in patients with Brugada syndrome have not been clarified. Therefore, in a retrospective, single-center, follow-up study, we assessed the incidence and clinical implications of supraventricular tachyarrhythmia in patients with Brugada syndrome.
Results The study group comprised 66 men and 3 women with a mean age of 50.7±13.6yr (range, 24–76yr). Forty-seven patients had spontaneous Brugada type 1 ECG, and 22 had drug-induced Brugada type 1 ECG (conversion from type 2 [n=12] or type 3 [n=10]). The clinical, genetic, electrocardiographic, and electrophysiologic characteristics of the study patients are shown in Tables 1 and 2. Eleven patients were symptomatic (syncope, n=3; presyncope, n=2; aborted SCD, n=6; mean age, 52.5±14.2yr [range, 25–76yr]), and 57 patients were asymptomatic (mean age, 50.3±13.5yr [range, 24–75yr]). Five patients had a family history of SCD. An SCN5A gene mutation was found in 2 patients (5.1%). Supraventricular tachyarrhythmias were found in 7 patients (supraventricular tachycardia, 2 patients; paroxysmal AF, 2 patients) (10.1%). The prevalence of a spontaneous type 1 Brugada ECG and symptoms (history of syncope, presyncope, documented ventricular tachyarrhythmia, or aborted SCD) were significantly higher, and QRS duration was significantly longer, in patients without supraventricular tachyarrhythmia than in those with supraventricular tachyarrhythmia. The PR and AH intervals were longer in patients without than in those with supraventricular tachyarrhythmia; however, the differences were not statistically significant (Table 2).
Discussion Supraventricular arrhythmias are being increasingly recognized in patients with Brugada syndrome. Incidences of spontaneous supraventricular tachyarrhythmia of between 6% and 39% have been reported . The reported inducibility of supraventricular tachyarrhythmia ranges from 3% to 100% . Bordachar et al.  suggested that the disease process is more advanced in patients with Brugada syndrome and supraventricular tachyarrhythmia. Sacher et al. conducted one of the largest studies to yield data on supraventricular tachyarrhythmias in patients with Brugada syndrome . In this study, supraventricular tachyarrhythmias were documented in 32 of their 220 patients, with 23 of the 32 (10% of the total patients) having AF. AF is the most common atrial arrhythmia found in Brugada syndrome, with a prevalence varying between 10% and 39% (Table 4) [1,10,11,15–17], although a few cases of associated AVNRT and atrioventricular reentrant tachycardia with an accessory pathway have also been noted [9,18–21]. These data indicate that, in patients with supraventricular tachyarrhythmia, Brugada syndrome should be added to the list of possible causes of syncope or aborted SCD, even in the presence of an accessory pathway. In our patient series, the incidence of AF (2 of 69 [2.9%]) was lower than the previously reported incidences (Table 4); however, in the present study, AF was the first clinical manifestation before the diagnosis of manifest or latent Brugada syndrome. Pappone et al.  reported that 3.2% (11 of 346 patients) of new-onset AF as the first clinical manifestation showed spontaneous or drug-induced type 1 Brugada ECG pattern, and Rodríguez-Mañero et al.  found that in 5.7% (35 of 611) of patients, AF was diagnosed before the identification of manifest or latent Brugada syndrome. In the present study, AF was the first clinical manifestation, and type 1 Brugada ECG was unmasked by the initiation of a class I antiarrhythmic drug. Therefore, our data are similar to those of these 2 reports with regard to the number of patients presenting with AF as the first manifestation of latent Brugada syndrome.